The present invention relates in general to lint condensers and the like for separating cotton or other fibrous materials from a stream of air, such as lint condensers in current use in the cotton industry which are adapted to collect and remove lint, fibers and like material from an air current by the use of a moving foraminous screen upon which the lint or fiber is deposited by the air current. More particularly, the invention relates to lint condensers and the like in which subatmospheric pressure conditions are maintained in the condenser housing in the zone immediately outwardly surrounding the surface of the condenser drum or rotating screen and wherein means are provided for humidifying the lint in the condenser so that the lint discharged to the bale press is automatically maintained at a desired range of moisture content.
It is very common practice to convey lint cotton from a plurality of gin stands, where the lint is separated from the seeds, by means of a current of air through a lint flue to a condenser, frequently referred to as a battery condenser, serving a number of such gin stands, where the lint or fiber which is air conveyed into the condenser housing or casing is deposited on a screen mounted in the housing and forms a bat which is doffed from the screen and discharged through a lint slide to the baling press. A typical condenser comprises a rotary screen drum mounted in the condenser housing into which the fiber laden current of air is conducted, the arrangement being such that the current is directed through the peripheral screen surface of the drum and is discharged axially through one or both of the ends of the drum through an opening or openings in the side of the housing. During such travel, the lint or fiber is deposited on the screen surface and is carried by the rotary motion of the drum into the range of operation of a pair of doffing rolls which strip the fiber from the drum and discharge it from the apparatus, usually down a lint slide. It is customary to locate curved sealing strips or flashing at each side or head of the condenser housing adjacent the ends of the rotating screen drum extending in a circular path concentric with the drum axis and conforming closely to the shape of the ends of the screen drum to contact the rotating drum surface and form a seal between the rotating drum and the heads of the condenser housing.
Prior to the development of lint cleaning in gin installations, the condenser serving the gin stands received the lint and conveying air under a slightly positive pressure generated by the mechanism used to doff the lint from the gin saws in the gin stands. This operation of the condenser under slightly positive pressure or superatmospheric pressure permitted the use of large doffing rollers which allowed some air to leak between the rollers, helping to thread the lint bat between the rollers. The introduction of lint cleaners between the gin stands and condenser made it necessary to place the condensing chamber under vacuum or subatmospheric pressure in order to convey the lint from the lint cleaner to the condenser. The amount of vacuum or subatmospheric pressure needed varied with the type of lint cleaning being used. The pressure difference inside and outside the condensing chamber presented problems in getting the lint bat to thread between the doffing rollers.
It will be appreciated that the introduction of high vacuum cleaners introduced considerable problems, particularly in regard to arranging the doffing rollers so that they would both seal against the high vacuum and deliver a lint bat to the atmospheric pressure conditions existing in the lint slide which received the bat from the doffing rollers of the condenser. While attempts have been made to provide doffing rollers which are arranged to float, so that they may move away from the screen and away from a companion fixed roller as the bat thickness varies, to attempt to obtain the desired seal between the doffing rollers against the high vacuum, considerable complications have been introduced by providing appropriate drive for such a floating doffing roller. As the handling capacity of battery condensers has increased from about 10 bales per hour in the early 1950's to 30 to 40 bales per hour at the present time, the speed of the condenser screen drum and the doffing rollers have been increased in proportion, resulting in more problems with gear wear and damage to the screen surface in case of chokes.
A further complication has resulted from use of small diameter rollers having to run close to the screen drum, because sealing of the joint between the screen drum and the heads of the condenser formed by the sides of the condenser casing adjacent the doffing rollers becomes difficult, as the old customary methods of sealing could not be used in this construction and alternate methods have been troublesome. If one attempts to seal the space between the rotating screen drum and head or side wall of the condenser casing by the usual flashing fixed to the head of the condenser and contacting the rotating drum surface, the contact between the rotating drum surface and the flashing results in lint fibers being picked up by the pinch point, and too often the fibers grow into a troublesome wad as the drum rotates. I propose to eliminate flashing between the condenser drum and the condenser head while still providing an effective seal against loss of lint through the space between the condenser drum and the condenser head by forming an air chamber between the end of the condenser head by forming an air chamber between the end of the condenser drum and the head of the condenser which permits air to flow from outside the condenser through the space between the end of the drum and the condenser head as a result of the high vacuum inside the condensing chamber, so that the air flow thus produced effectively seals the space against loss of lint through the space.
Due to a number of recent developments, it has become highly desirable to be able to control the moisture of the lint as it is packaged in the baling presses to which the lint is delivered from the condenser. Textile mills prefer cotton to have a moisture level in the range of about 7% to 8% in order for the cotton to be at an optimum condition for processing at the textile mill. The old custom of using jute bale coverings permitted the lint in the bale to come to equilibrium at such moisture levels in a humidified warehouse or in ambient conditions at the mill warehouse. However, the search for better packages for cotton has led to the frequent use in recent years of sealed polyethylene bags. This has made it highly desirable to control the moisture of the lint as it is being packaged at the gin house because cotton in such sealed packages will not have a chance to regain moisture in the warehouse at the textile mill site. It therefore becomes extremely important that the moisture content of the cotton as it is discharged from the condenser into the baling press for packaging be at the desired moisture level for mill processing, since the cotton will not have a chance to regain moisture by storage under ambient conditions which will bring it to the desired level.
It will be understood that it is not uncommon for the lint to reach the condenser with only about 5% moisture and it may be as low as about 4% moisture. This is due to the fact that the seed cotton conditioning process, which is necessary to efficiently extract foreign matter, brings the lint moisture down below 6%. Under ambient conditions existing in much of the cotton belt, the humidity is low enough to permit further removal of moisture from the lint as it is conveyed by ambient air to the condenser. Thus it becomes desirable to add about 3% moisture to the cotton at the condenser, if the cotton reaches the condenser with only about 5% moisture, in order to insure that the moisture content be near the optimum level of about 8% when the cotton is packaged, so that it will have the optimum moisture level for processing at the textile mill. Further, by adding 3% moisture to the cotton, the weight of a 500 pound bale would be increased to about 515 pounds, which would add $8.00 to $10.00 to value of the bale at current prices. Such addition of moisture, with consequent increase in bale price, is highly acceptable in the trade because of the preference of the textile mills for the higher moisture cotton in the processing line at the textile mill.
Another significant factor in favor of the higher moisture is the reduced compression load on the baling press. Modern gins produce a universal density bale with the density of about 28 pounds per cubic foot. This requires a press capable of up to 700 tons of compression capacity with low moisture lint, while with the 7% to 8% moisture level, the load may be reduced by as much as 1/3.
An object of the present invention, therefore, is the provision of a novel condenser for receiving air borne lint such as cotton or other fibrous material from an air stream and forming a bat therefrom for delivery to a packaging press, wherein the condenser chamber outwardly surrounding the rotating screen drum is at subatmospheric pressure and means are provided to monitor the moisture level of the cotton bat being delivered by the condenser and supply air of controlled high humidity to the condenser chamber to raise the lint moisture to a desired level of about 8% moisture.
Another object of the present invention is the provision of a condenser for lint cotton or the like as described in the preceding paragraph, wherein the high humidity air is passed through the bat and through the screen drum ahead of the doffing rollers to raise the moisture level of the cotton to the desired level.
Another object of the present invention is the provision of a novel condenser for lint cotton or the like as described in either of the two immediately preceding paragraphs, wherein a doffing arrangement is provided to wipe the condenser screen in order to maintain the condenser screen free of moisture condensate which may cause lint to stick to the condenser, and wherein a further set of doffing rollers are provided to receive the formed bat from the screen doffing rollers and act as a seal against the pressure difference between the subatmospheric pressure in the condenser chamber and the atmospheric pressure externally of the condenser.
Another object of the present invention is the provision of a novel condenser for lint cotton and the like wherein the condenser chamber outwardly surrounding the screen drum is at subatmospheric pressure and wherein air nozzle means are provided adjacent the end of the screen drum providing a circular air jet causing air flow adjacent the opening between the end of the rotating drum and the head plate or side wall of the condenser which will prevent any fibers from passing through this opening and thereby provide an effective seal without use of flashing which seats against either the rotating drum or the head plate of the condenser casing.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.